Method and device for producing veneer and veneered parts and veneer and veneered parts

ABSTRACT

The invention aims at improving a method and a device ( 17 ) for the production of veneers ( 1 ) and veneered parts ( 13 ) and to veneers ( 1 ) and veneered parts ( 13 ). To this end, a sealing layer ( 2 ) is applied on the surface of the veneer ( 1 ) before further processing. The device ( 17 ) includes a veneer producing device known per se, a finishing station ( 6 ), a transporting device ( 5 ) and a polishing station ( 8 ).

[0001] The invention relates to a method and a device for producingveneer and veneered parts.

[0002] Veneer is used in large measure in the furniture andwood-processing industry. For example, veneer finds application in thefield of wrapping, for example for wall connection strips, for surfacelamination e.g. for furniture surfaces, for planks, tables etc. or inedge coating or edge gluing, for example for straight edges,soft-forming or post-forming with table boards, furniture doors or thelike. For this purpose the veneer itself is first produced, for exampleby means of stripping from a solid piece of wood. These large areaveneer sheets are then either placed in temporary storage, for examplewound up into a veneer roll or are immediately further processed. In thefinishing of the veneer for production of veneered parts the veneer isglued onto the wooden support or derived timber product support and thenthe half finished part is sanded and painted or else directly painted.The painting operation is costly, since not only surfaces, but alsoprofile geometries of the veneer paneling profile have to be painted.The profiles can be bonded with the veneer in the soft-forming processon an edge banding machine, in the post-forming process or in anotherway. The paints used in painting must as a rule be applied in multiplecoats, which calls for expensive process technology and correspondingfloor space requirements.

[0003] One widespread painting system involves ultraviolet hardenedpaints, which are usually applied by roller coating, more rarely inspray application on the parts. The subsequent curing process occurswith ultraviolet light or ultraviolet lamps. The mechanical cost inpainting with ultraviolet paints is very high and necessitates verylarge floor space requirements. The large floor space requirements arealso due to the fact that the painting process with ultraviolet curingsystems usually require several applications—in practice three to fourapplications are common. With each coat of paint, due to the viscosityand especially due to the ultraviolet curing only approximately 10 to 20my layers can be applied, which is why several paint applications arenecessary. Ultraviolet lamps and the necessary energy for curing arequite expensive.

[0004] Other painting systems, such as 2 package urethane coatingpaints, nitrocellulose lacquers or water-based paints must also beapplied in several layers. Fillers, primers and if necessaryintermediate sanding are also always necessary and make the surfacecoating complex and is mechanically very time-consuming and costly.

[0005] It is the objective of the invention to advantageously furtherdevelop the state of the art.

[0006] This task is solved with the features of the independent claims.

[0007] In a method for producing one or multiple-ply veneer it isproposed that the a sealing layer be applied to the surface of theveneer first produced in known fashion prior to further processing intoveneered parts. The veneers produced in known fashion are present assheets or rolls. By means of applying a sealing layer to theselarge-area veneers the veneer is completely finished in its surface,which corresponds to the later face, before the veneer is glued,covered, laminated, or the like. As a result only one area coating orfinishing of the veneer surface is necessary, which represents asignificant simplification. One obtains thus a large-area “finishedveneer”, which in subsequent processing into veneered parts, which cantake place either after an intermediate storage on a veneer roll orimmediately following, is only bonded with the wooden or derived timberproduct support, without an expensive surface finishing of the veneeredparts through profile geometries being necessary.

[0008] In an advantageous development of the invention's productionmethod for veneer the sealing layer is applied as a water-free andsolvent-free atmospheric moisture curing cold-hardening hot-melt sealinglayer on polyurethane basis. The water- and solvent-free cold-hardeninghot-melt sealing layer is applied to the surface to be sealed at atemperature of above 100° C., about 100° C. to 140° C. In the processabout 50 to 100 g of cold-hardening hot-melt sealing is applied persquare meter to the surface to be coated. The cold-hardening hot-meltsealing usually has a density of approximately 1.1 g/m² and a viscosityaccording to Brookfield at 120° C. of about 4,000 mPas. However,significantly higher viscosities of the cold-hardening hot-melt sealinglayer of up to 30,000 mPas are conceivable. It is favorable to apply thecold-hardening hot-melt sealing layer under the exclusion of air andshielding from atmospheric pressure, to prevent premature reactions. Thelayer can for example be scraped on, rolled on, sprayed on or applied bymeans of a nozzle or air jet. Even in cured state as a 100% solid thecold-hardening hot-melt sealing layer still exhibits a certain residualelasticity. A cold-hardening hot-melt sealing layer has proved to beadvantageous for the coating of veneer, because it can be applied in asingle coating to the surface of the veneer. The remaining residualelasticity of the sealing layer makes possible the subsequent gluingprocesses, even around profile geometries. In the process the sealinglayer effects an additional stabilization of the veneer surface, whichprevents cracks in the surface. As a result is also possible, dependingon the subsequent use of the veneer (surface lamination, edge gluing,profile wrapping) to dispense with the fiber mat usually glued to therear side of the veneer prior to further processing of the parts to beveneered, i.e. along with the material costs for fiber mat and adhesivefor gluing the fiber mat the processor saves a complete processing step.Above all with simple profile geometries and surface laminations it isadvantageously possible to dispense with fiber mat. In addition to theseadvantages, the cold-hardening hot-melt sealing layer exhibits a high UVstability, a high degree of hardness, resistance to scratches and a veryhigh resistance to shock. The processing of the cold-hardening hot-meltsealing layer requires only slight machine investments and little spacein comparison to conventional painting plants. Coating withcold-hardening hot-melt sealing represents a simple hot-cold reactionwith subsequent cross-linking process with the help of moisture from theair or the material, without an ultraviolet or electron ray curing orthe like being necessary.

[0009] An improvement of the surface properties of the cold-hardeninghot-melt sealing layer can be achieved by polishing the cold-hardeninghot-melt sealing layer after application to the surface of the veneer.As a result of this, unevenness of the surface is avoided, which cancome into being merely by means of the application of the hotcold-hardening hot-melt sealing, and the result is an even smoothersurface. It is also possible then to work with smaller materialquantities between 50 and 100 g/m² on the cold-hardening hot-meltsealing.

[0010] It is advantageous to add heat once more to the surface of thecold-hardening hot-melt sealing layer between the application and thepolishing, in order to further improve the results of the polishing.Favorably the polishing takes place by means of a roller, for example asteel roller, which if necessary can be provided with a polyurethanecoating.

[0011] It is particularly advantageous if the roller is sprinkled with astripping agent during the polishing process. In this way oneeffectively prevents the still not cured cold-hardening hot-melt sealinglayer from separating on the part to be sealed and sticking to theroller. Preferably the stripping agent is applied as a solvent-free andlow-viscosity agent on a paraffin wax basis. Such an agent on the onehand prevents the sticking of the cold-hardening hot-melt sealing layerto the roller and in addition the surface of the cold-hardening hot-meltsealing layer becomes significantly smoother and immediately block-free.The stripping agent on paraffin wax basis is clear and has for example adensity of approximately 0.85 g/cm³ as well as a viscosity at 20° C.according to Brookfield of about 34 mPas. A viscosity range between 30and 500 mPas is conceivable. The application quantity amounts to about20 to 35 g/m².

[0012] The stripping agent is for example applied to the roller in aspray process or vacuum spray process. However, it is preferred to applythe stripping agent to the roller by means of soaked felt, whichrepresents an especially easy and secure option for creating a uniform,thin film of stripping agent during the polishing of the cold-hardeninghot-melt sealing layer.

[0013] A device for producing veneer with a sealing layer on its surfacecontains a veneer producing device known per se, a finishing station, atransporting device and a polishing station. In the process it isfavorable if there is a heating device arranged between the finishingstation and the polishing station.

[0014] In a preferred embodiment of the device the polishing stationcontains at least one roller, which preferably is a steel roller anddepending on the application situation exhibits a polyurethane coating.In addition it is advantageous if the roller can be sprinkled with astripping agent. This stripping agent is for example an above describedagent on paraffin wax basis. A spray device, vacuum spray device or asoaked piece of felt can for example be used to sprinkle the roller withthe stripping agent.

[0015] In a method for producing a veneered part a single-ply ormultiple-ply veneer as per the invention is glued to a wooden or derivedtimber product support. As already explained, as a result of this it ispossible, depending on the application situation, to forego the gluingof a fiber mat to the rear of the veneer prior to further processing,without fearing that cracks will develop in the veneer surface duringcoating of profile geometries. Additionally, it is no longer necessaryto finish the surface of the veneered part by means of sanding andpainting.

[0016] In the drawing the invention is explained using an exemplifiedembodiment. The figures show the following:

[0017]FIG. 1 shows a schematic section of veneer as per the inventionwith a sealing layer on the surface,

[0018]FIG. 2 shows a device for producing veneer with a sealing layer onthe surface,

[0019]FIG. 3 shows an enlarged section of a veneered part as opposed tothe section in FIG. 1,

[0020]FIG. 4 shows a different device for coating veneer rolls.

[0021]FIG. 1 shows a section of veneer 1. On the top side of the veneer1 a sealing layer 2 is applied made of a water-free and solvent-freecold-hardening hot-melt sealing layer curing with the atmosphericpressure on polyurethane, which has been polished during productionafter application by means of a roller sprinkled with stripping agent.This polishing operation results in a particularly smooth surface of thesealing layer which is indicated by means of the continuous line 3.

[0022]FIG. 2 shows a diagramatically represented production line 4 forcontinuous production of the invention's veneer 1. The production line 4contains a veneer producing device that is known per se and is notshown, in which the veneer for example is produced by means of strippingfrom a solid piece of wood. However, it would also be possible to addconventional veneers without surface coating, which are for examplerolled up in a veneer roll, to the production line for a surfacecoating. A transporting device 5 for the veneer to be coated transportsthe veneer 1 first from the veneer producing device to a finishingstation 6. At the finishing station 6 the cold-hardening hot-meltsealing layer is heated to at least 100° C. under the exclusion of airand shielding from atmospheric pressure and then pumped by a pump devicenot shown in the figure into a heated hose, conducted through the hoseto a finishing station, for example an air jet 7 and applied to theveneer 1 by the air jet.

[0023] The cold-hardening hot-melt sealing layer is a water-free andsolvent-free cold-hardening hot-melt sealing layer on polyurethane basiscuring with the atmospheric pressure, which is applied to the surface tobe sealed at a temperature above 100° C., for example 100° C. to 140° C.In the process about 50 to 100 g of cold-hardening hot-melt sealing isapplied per square meter of surface to be coated. The cold-hardeninghot-melt sealing normally has a density of about 1.1 g/m² and aviscosity according to Brookfield at 120° C. of about 4,000 mPas,whereby a higher viscosity of up to 30,000 mPas is also conceivable. Itis favorable to apply the cold-hardening hot-melt sealing layer underthe exclusion of air and shielding from atmospheric pressure to avoid apremature reaction. The layer can for example be scraped on, rolled on,sprayed on or applied by means of a nozzle or air jet.

[0024] The veneer 1 coated with the cold-hardening hot-melt sealinglayer is further transported from the finishing station to fixing andpolishing station 8. Between the application of the cold-hardeninghot-melt sealing layer 2 and the fixing station 8 the surface of thecold-hardening hot-melt sealing layer is furnished with heat via anindicated heating device 9, in order to keep the cold-hardening hot-meltsealing layer at least viscous.

[0025] At the fixing and polishing station 8 there are 3 pivoted rollers10 that can be adjusted in height if necessary. The rollers are providedwith a polyurethane coating. Above each of the rollers 10 is a piecefelt 11 that the rollers are in contact with, said felt being soakedwith a stripping agent on paraffin wax basis. By means of turning therollers the felt applies a uniformly low quantity of the stripping agentas a thin layer to the surface of the rollers 10, which these pass alongupon contact with the surface of the cold-hardening hot-melt sealinglayer 2. By means of the stripping agent the surface of thecold-hardening hot-melt sealing layer 2 is immediately block-free andsupports the polishing operation.

[0026] The coated and polished veneers are further transported by thetransporting device 6 from the fixing and polishing station 8 andnormally placed in temporary storage for about three to four days forcross-linking of the cold-hardening hot-melt sealing layer 2. Aftercomplete cross-linking the cold-hardening hot-melt sealing layer 2 formsa sealing layer solidly bound with the veneer 1 on the surface, whichrepresents a 100% solid body and whose thickness during the applicationcan be set to between 5 and 150 my depending on requirements. A furtherprocessing of the veneer 1 is then possible for production of veneeredparts.

[0027]FIG. 3 shows a veneered part 13. Veneers 1, 15, 16 are glued to awooden or timber product derivative support 14. On the surface of theveneers 1, 15, 16 a sealing layer 2 is applied on the face as awater-free and solvent-free atmospheric moisture cross-linkingcold-hardening hot-melt sealing layer on polyurethane basis, as has beenexplained in greater detail in FIG. 1. The veneer 15 has, for example,glued on by means of a soft-forming method on a edge gluing machine notshown in the figure. The residual elasticity contained in the reactedcold-hardening hot-melt sealing layer holds the surface of the veneer 1together, so that cracks or gaps are avoided in veneer 1. For thisreason a fiber mat glued to the rear of the veneer 1 can be dispensedwith.

[0028] Basically the veneer 1 furnished with a sealing layer 2 can beglued in any way. It is possible to take the veneer 1 provided with asealing layer 2 after first coating of the surface of the veneer 1 on aseparate piece of equipment and then roll it up again into a veneer rolland further process it at a later time. In addition, a furtherprocessing immediately after the coating is conceivable for example in apass on a wrapping machine, an edge gluing machine, a post-formingmachine or a surface laminating machine.

[0029] A device 17 for coating veneer rolls is diagramaticallyrepresented in FIG. 4. The uncoated veneer 1 is removed by a deliveryspool 18 and fed to an application unit 19, in which via rollers 20 awater-free and solvent free atmospheric moisture curing cold-hardeninghot-melt sealing layer on polyurethane basis is applied. Passing througha heating source 21, the veneer is fed to the fixing and polishingstation arranged in a housing 22.

[0030] Located in the housing are pressure and polishing roller pairs23, 24, 25, by means of which the applied cold-hardening hot-meltsealing layer on the veneer is pressed and polished. The roller pairs23, 24, between which an additional heating source 26 is arranged, aresprinkled during the pressing and polishing operation by means of apiece of felt 27 with a stripping agent on paraffin wax basis alreadydescribed in greater detail above. By means of the already describedeffect of the stripping agent the cold-hardening hot-melt sealing layerapplied on the veneer is immediately block-free, so that the rolled upveneer is prevented from adhering to itself. Additionally, a coolingzone 28 indicated by arrows is arranged between the roller pairs 24 and25. After leaving the housing 22 of the fixing and polishing station thecoated veneer is rolled back up into a veneer roll 30 by means of aguide roller 29. The cold-hardening hot-melt sealing layer of the rolledup veneer then has the opportunity to completely cross-link chemically.

[0031] It is possible to use the described device to coat uncoatedveneer rolls in an automatic and continuous process and roll them up.

1. Method for producing single-ply or multi-ply veneer which is producedin per se known manner, characterized by the fact that a sealing layeris applied to the surface of the veneer prior to further processing. 2.Method according to claim 1, characterized by the fact that the sealinglayer is applied as a water-free and solvent-free atmospheric moisturecuring cold-hardening hot-melt sealing layer on polyurethane basis. 3.Method according to claim 2, characterized by the fact that thecold-hardening hot-melt sealing layer is polished after application. 4.Method according to claim 3, characterized by the fact that between theapplication and polishing of the surface heat is added to thecold-hardening hot-melt sealing layer.
 5. Method according to claim 34,characterized by the fact that the polishing of the cold-hardeninghot-melt sealing layer occurs by means of at least one roller.
 6. Methodaccording to claim 5, characterized by the fact that a steel roller isused.
 7. Method according to claim 5, characterized by the fact that theroller exhibits a polyurethane coating.
 8. Method according to claim 5,characterized by the fact that the roller is sprinkled with a strippingagent during polishing.
 9. Method according to claim 8, characterized bythe fact that the stripping agent is applied as a solvent-free and lowviscosity agent on a paraffin wax basis.
 10. Method according to claim8, characterized by the fact that the stripping agent is applied to theroller in a spraying procedure.
 11. Method according to claim 8,characterized by the fact that the stripping agent is applied in thevacuum spraying procedure.
 12. Method according to claim 8,characterized by the fact that the stripping agent applied to the rollerby means of a soaked piece of felt.
 13. Single-ply or multi-ply veneer,which is produced in a manner known per se, characterized by the factthat a sealing layer is applied to the surface of the veneer.
 14. Veneeraccording to claim 13, characterized by the fact that the sealing layeris designed as a water-free and solvent-free atmospheric moisture curingcold-hardening hot-melt sealing layer on polyurethane basis.
 15. Veneeraccording to claim 14, characterized by the fact that the cold-hardeninghot-melt sealing layer applied to the surface is polished.
 16. Veneeraccording to claim 15, characterized by the fact that the cold-hardeninghot-melt sealing layer is polished by means of at least one roller. 17.Veneer according to claim 16, characterized by the fact that thecold-hardening hot-melt sealing layer is polished by means of a steelroller.
 18. Veneer according to claim 16, characterized by the fact thatthe roller exhibits a polyurethane coating.
 19. Veneer according toclaim 16, characterized by the fact that cold-hardening hot-melt sealinglayer is polished by means of a roller sprinkled with a stripping agent.20. Veneer according to claim 19, characterized by the fact that thestripping agent is a solvent-free and low viscosity agent on a paraffinwax basis.
 21. Method for producing a veneered part, in which asingle-ply or multi-ply veneer is glued to a wooden support or timberderived product support with a sealing layer according to claim 13applied to the surface of the veneer.
 22. Veneered part with a wooden ortimber derived product support, to which a veneer is glued,characterized by the fact that the veneer is formed according to claim13.
 23. Device for producing veneer with a sealing layer on a surface,which contains a veneer producing device known per se, a finishingstation, a transporting device and a polishing station.
 24. Deviceaccording to claim 23, characterized by the fact that a heating deviceis arranged between the finishing station and the polishing station. 25.Device according to claim 23, characterized by the fact that thepolishing station contains at least one roller.
 26. Device according toclaim 25, characterized by the fact that the roller is a steel roller.27. Device according to claim 25, characterized by the fact that theroller exhibits a polyurethane coating.
 28. Device according to claim25, characterized by the fact that the roller can be sprinkled with astripping agent.
 29. Device according to claim 28, characterized by thefact that a spraying device is provided for sprinkling the roller withthe stripping agent.
 30. Device according to claim 28, characterized bythe fact that a vacuum spray device is provided for sprinkling theroller with the stripping agent.
 31. Device according to claim 28,characterized by the fact that a soaked piece of felt is provided forsprinkling the roller (10) with the stripping agent.